Disintegration of many concrete pavements (D-cracking, popouts, etc.) exposed to freezing and thawing is often connected with poor physical quality of aggregates used in the concrete. Inability to differentiate between good and poor quality aggregates is due to the lack of appropriate laboratory techniques for aggregate evaluation. A growing shortage of easily available sources of good quality aggregates highlights the need for aggregate classification. A new rapid laboratory test, called RAO-Method, as well as a new pore size distribution index based on the mercury intrusion porosimetry (MIP) analysis, has been proposed to meet engineers' expectations in the field of aggregate classification. An analysis of some research data of the RAO and MIP tests is presented in this paper to illustrate practical usefulness of the techniques. Results of long-term observations of concrete blocks subjected to outdoor conditions and the results of the new laboratory tests of the aggregates previously used in the blocks were compared. The new tests seem to provide means for more successful evaluation of coarse aggregates for purposes of diagnostics, design, and prediction of service life of concrete.

Presents basic information on a newly developed electrically conductive concrete. The concrete differs from previous inventions in that both high conductivity and mechanical strength are simultaneously achieved. The electrical and mechanical properties of the conductive concrete developed at Institute for Research in Construction, National Research Council of Canada are given. The material has superior electrical conductivity values and excellent mechanical strength. Experimental results of a laboratory-scale study on the application of conductive concrete to deicing and/or snow melting are presented in this paper. The results indicate that heat can be uniformly produced by the conductive concrete heating element when the element is activated by an external electric power supply. The new method is effective for deicing purposes. Power output of the conductive concrete heating element is stable over a wide range of temperature. The minimum heater power output required for deicing at various air temperatures was determined. This value is linearly dependent on the air temperature, ranging from 150 to 855 W/m 2 as air temperature varies from -5 C to -30 C.

For years, the concrete industry has used ultimate compressive strength and elastic modulus as principal design and analysis tools. This can be very misleading when cracking and failure are evaluated. With modern concrete that include roller-compacted concrete (RCC) and lower strength mass applications, cracking that is serious may not occur until the concrete is strained well beyond the elastic region. Two things are needed to resolve this problem. First, a new property called the "ultimate modulus" should be determined, along with the elastic modulus. If these values are nearly the same, the concrete is brittle and may have a low strain capacity, even if it has a high strength. If the ultimate modulus is much lower than the elastic modulus, the material is "tough" and may have a high strain capacity despite a low strength. Examples are given in which deliberately designing a lower strength concrete has resulted in a much higher strain capacity. In one case with RCC, a mixture with five times less strength resulted in a tensile strain capacity (and resistance to thermal cracking) that was three times greater. Second, there should be a better understanding of the relationships between strain capacity, strength, and modulus (ultimate and elastic) in compression as compared to those material properties in tension. With the broader range of concrete mixtures possible in today's concretes (RCC being an example), the ratio between split cylinder tensile strength and compressive strength may be twice as high for a lower strength mixture than it is for a higher strength mixture. Somewhat offsetting this is the fact that the conversion factors from split tensile strength or flexural strength to direct tensile strength are substantially smaller for low strength concretes and greater (exponentially) for high-strength concretes. When only concretes in the compressive strength range of about 20 to 50 MPa are considered, the adjustment factor happens to be about one, so this phenomenon has not been obvious or very important in the past.

Silica fume has been available commercially in the United States for over 10 years. Until recently, there has not been a well-accepted consensus specification for it. This paper deals with the question of a specification for silica fume for use in concrete by reviewing the following areas. 1. ASTM and AASHTO efforts to develop a specification for silica fume are described. The author's comments on these documents are presented. 2. The status of international efforts to develop silica fume specifications is reviewed. Work from Australia, Canada, Norway, RILEM, South Africa, and other European countries is reviewed to indicate the direction that is being taken outside the United States. 3. Recommendations, based upon the author's experience with silica fume since its introduction to the United States, for what a specification for silica fume for use in concrete should include are presented. The use of silica fume is increasing every year. Some engineers, particularly those in public agencies, have been hesitant to use the material because of the lack of a standard specification. Most engineers wanting to use silica fume have developed their own specification for silica fume with provisions that may have little or no relationship to the performance of the material in concrete. A consensus needs to be established to increase the confidence of specifiers wanting to use silica fume.

The Japanese economy has been highly developed through foreign trade. Port facilities have been supporting this economic growth; many concrete port structures have been constructed and maintained during the past few decades. Recently, various social and economical demands have required port facilities to be multi-functional. New facilities are being constructed to meet this trend. These changes include new types of breakwaters, revetment, and undersea tunnels which improve aesthetics and reduce cost, labor, and construction time. Fresh concrete used in the construction of these new types of structures is often required to have high flowability and to be self-compactible because of the complicated shape and densely arranged reinforcements of these structures. To meet these demands, the authors have developed super workable concrete using viscous admixture (segregation-reducing admixture) and super plasticizer. In this paper, the mix design and material properties of this supe rworkable concrete and examples of its application to new port concrete structures are presented.